I played with BikeGeo a bit and unfortunately it requires head tube and fork leangth. That makes it a little hard to work off of some of the commonly supplied specs. interesting that it dose not ask for seat tube measurements, which i get because most seat tubes are not measures C to C. It would be nice to be able to link values so that raising the top tube vertically would increase the seat and head tube lengths, or if you had the seat tube C to C you could determine the head tube.